Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$21.34	13.760%	$24.2764	$24.28	$24.30	$24.30
Purchase #2	$46.25	11.107%	$51.387	$51.39	$51.40	$51.40
Purchase #3	$42.34	3.401%	$43.78	$43.78	$43.80	$43.80
Purchase #4	$125.30	4.145%	$130.4937	$130.49	$130.50	$130.50
Purchase #5	$233.48	13.464%	$264.9157	$264.92	$264.90	$264.90
Purchase #6	$20.38	8.768%	$22.1669	$22.17	$22.15	$22.20
Purchase #7	$111.94	4.296%	$116.7489	$116.75	$116.75	$116.70
7 purchase totals =	$601.03		$653.7686	$653.78	$653.80	$653.80